INTEGRATED LED AND LED DRIVER UNITS AND METHODS FOR FABRICATING THE SAME
Integrated LED and LED driver units and methods for fabricating integrated LED and LED driver units and products with a plurality of integrated LED and LED driver units are provided. In an embodiment, a method for fabricating an integrated LED and LED driver includes forming an LED driver in a first substrate, wherein the first substrate is a semiconductor substrate. The method include forming a bond pad over a top surface of the semiconductor substrate and electrically connected to the LED driver. Also, the method includes forming an LED on a second substrate. Further, the method includes directly coupling the LED to the bond pad.
The technical field generally relates to light emitting diodes (LEDs), and more particularly relates to LEDs and their electrical connection to LED driver devices.
BACKGROUNDThe light-emitting diode (LED) is a common lighting appliance in increasing use. In comparison with traditional incandescent light bulbs, LEDs have higher luminous efficiency and power-saving features. However, LEDs are conductive only in a single direction and thus require specialized LED driver circuits.
Typically, LEDs are formed and packaged separately from their LED driver electronics. One method for packaging LEDs and LED drivers together in a single package would connect the LED driver to an LED by a through silicon via (TSV) that passes through a silicon interposer. However, the use of silicon interposers may increase package costs. For example, package costs for LEDs could be higher than the cost of the semiconductor LED.
Accordingly, it is desirable to provide simpler and more efficient LED and CMOS compatible integration schemes and enabling methodology. Also, it is desirable to provide improved methods for fabricating LEDs and LED drivers. It is desirable to provide integrated LED and LED driver units and methods for fabricating integrated LED and LED driver units that reduce packaging costs and provide improved performance. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.
BRIEF SUMMARYIntegrated LED and LED driver units and methods for fabricating integrated LED and LED driver units and products with a plurality of integrated LED and LED driver units are provided. In an embodiment, a method for fabricating an integrated LED and LED driver includes forming an LED driver in a first substrate, wherein the first substrate is a semiconductor substrate. The method include forming a bond pad over a top surface of the semiconductor substrate and electrically connected to the LED driver. Also, the method includes forming an LED on a second substrate. Further, the method includes directly coupling the LED to the bond pad.
In another exemplary embodiment, a method for fabricating a product with a plurality of integrated LED and LED driver units is provided. The method includes forming LED drivers in a first substrate, the first substrate being a semiconductor substrate. The method forms bond pads over the semiconductor substrate, wherein each bond pad is electrically connected to a respective LED driver. Also, the method forms LEDs on a second substrate. The method includes attaching each LED to a respective bond pad to form the product with the plurality of integrated LED and LED driver units.
In yet another exemplary embodiment, an integrated LED and LED driver unit is provided. The integrated LED and LED driver unit includes a semiconductor substrate and an integrated circuit (IC) including an LED driver in the semiconductor substrate and a first bond pad over the semiconductor substrate. The first bond pad is electrically connected to the LED driver. The integrated LED and LED driver unit further includes an LED having a first electrode in electrical contact with the first bond pad of the IC. The LED is directly coupled to the first bond pad and the LED driver is configured to control a current flowing through the LED.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The various embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the integrated LED and LED driver units or the methods for fabricating the integrated LED and LED driver units. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background or brief summary, or in the following detailed description.
For the sake of brevity, conventional techniques related to integrated circuit (IC) device and LED fabrication may not be described in detail herein. Moreover, the various tasks and processes described herein may be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. In particular, various steps in the fabrication of integrated circuits are well-known and so, in the interest of brevity, many conventional steps will only be mentioned briefly herein or will be omitted entirely without providing the well-known process details.
As used herein, it will be understood that when an element or layer is referred to as being “over” another element or layer, it may be directly on the other element or layer, or intervening elements or layers may be present. When an element or layer is referred to as being “on” another element or layer, it is directly on and in contact with the other element or layer. Further, spatially relative terms, such as “above”, “lower”, “upper”, “top” and the like, may be used herein for ease of description to describe one feature's relationship to another feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as being “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass either an orientation of above or an orientation of below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
In accordance with the various embodiments herein, integrated LED and LED driver units and methods for fabricating integrated LED and LED driver units are provided. The methods described herein provide for the formation and packaging of LEDs and the associated LED drivers together. As a result, packaging costs can be greatly reduced. Further, the methods described herein avoid use of silicon interposers and through silicon vias (TSVs) in silicon interposers. The Figures illustrate exemplary embodiments for integrated LED and LED driver units and for fabricating integrated LED and LED driver units.
As shown in
In
Portions of P—GaN layer 28 and active layer 26 are removed to expose a top surface of N—GaN layer 22. A dielectric layer 30 is deposited over the exposed surfaces and subsequently patterned (partially removed) to expose contact openings 32 to GaN layers 28 and 22. Dielectric layer 30 may be formed of silicon dioxide, silicon nitride, or the like. One or more metallization layers are formed and patterned to create anode 34 and cathode 36, which may include multiple metal layers. For example, to provide good electrical contact to P—GaN layers 28, the contact metal may be palladium, platinum, nickel, and the like. To provide good electrical contact to N—GaN layers 22, the contact metal may be titanium, aluminum, and the like. Additional metal layers may be laminated on top of the contact metal layers to provide a metal surface that is suitable for integration as discussed below. For example, a solderable metal stack such as titanium, nickel, and gold or silver may be laminated on top of the contact metal layers to provide a solderable metal surface.
A passivation layer 38 may be formed over dielectric layer 30 and over portions of anode 34 and cathode 36. Passivation layer 38 may be a dielectric material such as silicon dioxide, silicon nitride, polyimide, and the like. Openings 39 are formed in passivation layer 38 to allow for electrical contact to anode 34 and cathode 36.
As a result of the process shown in
While
In an exemplary embodiment, a dicing process (e.g. laser dicing, dicing with a diamond stylus, or dicing by sawing) is performed to separate the light emitting structure 40 into separate light emitting diodes (LEDs) 50. As shown, an exemplary dicing process separates the light emitting structure 40 into LEDs 50 while the substrate 12 remains at least partially uncut. The separation layer 14 may be cut by the dicing process. Each LED 50 has an upper surface 52 and a lower surface 54. As shown, the lower surface 54 of each LED 50 is in contact with the separation layer 14.
In
In
In an alternative embodiment, the separation of substrate 12 from light emitting structure 40 may be performed before light emitting structure 40 is diced into individual LEDs 50.
As shown in
LED driver devices 60, such as metal oxide field effect transistors (MOSFETs), are formed in the semiconductor substrate 12 according to conventional IC processing. Also, sensor devices 64, such as thermal or optical sensors formed from IC device elements, such as MOSFETs, resistors, or diodes, may be formed in the semiconductor substrate 62 according to conventional IC processing. A plurality of LED driver devices 60 and sensor devices 64 may be located in an IC 65. The semiconductor substrate 12 may include a plurality of ICs 65. In an exemplary embodiment, various metal and dielectric layer deposition and etching processes may be performed according to conventional IC processing to form a dielectric 66 with an embedded metallization structure 68 in selective contact with devices 60 and 64.
In
The method may continue with forming an under bump metallization (UBM) layer 82 over the final metal pads 70 and in contact with the exposed surfaces 78 of the final metal pads 70. An exemplary UBM layer 82 is formed of a laminated structure such as Ti/Pt/Au, Ti/Au, Ni/Au or Pt/Au or similar suitable metallization stacks. The UBM layer 82 may be formed by physical vapor deposition (PVD), evaporation, or other suitable processes. Attributes of the UBM layer for consideration include good mechanical adhesion to the final metal pads 70, a top surface that is compatible with the die attach process (discussed below), and good electrical contact between the die attach materials and the final metal pads 70.
As a result of the processing of
The method continues in
As fabricated in
Further, each of the plurality of LEDs 50 may be contacted to a respective IC 65 of the plurality of ICs 65 on substrate 62 to form a plurality of integrated LED and LED driver units 90 over substrate 62. An optional passivation layer may be formed over substrate 62, which includes LEDs 50 and ICs 65. The passivation layer may be a dielectric material that is substantially conformal with the underlying ICs and LEDs and may provide mechanical protection (e.g. scratch resistance) and protection against ingress of moisture and/or mobile ions. Contact windows may be formed in selected areas of the passivation layer to allow further packaging, as described below.
In
After the process of contacting selected LEDs 50 to selected ICs 65 is completed, a dicing process may be performed on the substrate 62 including the plurality of integrated LED and LED driver units 90 to singulate the integrated LED and LED driver units 90 from one another to form individual units. These individual units may then be mounted directly onto a printed circuit board (PCB) or placed into a package, using conventional packaging techniques.
The methods described herein may provide for the integration of multiple LEDs with a single IC, and that IC may contain a plurality of LED drivers. For example, an integrated LED and LED driver unit may include hundreds of LEDs and a single IC to form a micro display.
According to embodiments herein, the semiconductor substrate provides structural support to the LEDs such that the LEDs have sufficient mechanical integrity even after they are lifted off of their native substrate. Thus the combined units 90 are free-standing units that can be further packaged or mounted directly onto a PCB.
The embodiments herein provide units having an LED stacked directly on top of an IC that includes an LED driver. As a result, the units are provided with a smaller form factor as compared to conventional LED systems, which utilize separate packaging of the LED and the driver IC. In addition to reducing the form factor, direct stacking of the LED and driver IC may greatly reduce the overall system costs, by reducing the number of packages from two to one. Moreover, the direct connection of LED and driver IC is accomplished without using an interposer (i.e. another silicon substrate that is used to provide mechanical support and electrical interconnection of both the LED and driver IC).
In an embodiment, only the active portion of the LEDs is packaged on top of the LED driver IC. The active portion of the LEDs, i.e., layers 16, 22, 26, 28 and 38, has a total thickness of less than ten microns, such as about 4 microns. This is much thinner than the semiconductor substrate of the driver IC, which may be on the order of 100 microns or more, Thus, the stacking of the LED adds less than 10% to the height of the driver IC, and does not substantially inhibit the ability to singulate the units nor to package the units using conventional techniques.
In an exemplary embodiment, the methods described herein reduce processing costs as compared to conventional techniques, such as by reducing the number of packages and avoiding use of silicon interposers and TSVs on silicon interposers. Further, the detachable substrates used to form the LEDs 50 are reusable for the formation of additional LEDs, further reducing processing costs.
Also, the devices fabricated by the methods herein provide for packaged LEDs and LED drivers and other devices in close proximity, allowing for advanced control functions. Specifically, due to the reduced distance between LEDs and LED drivers provided herein, sensing of the LEDs may be performed by sensing devices in the device area housing the LED driver. For example, a thermal sensor may be included in the IC in close proximity to the attached LED, enabling real-time sensing and control of the LED temperature. In addition, the LED and LED driver units may exhibit reduced parasitic capacitance, resistance, and inductance as compared to conventional connections between LEDs and LED drivers, which may provide advantages such as increased switching speed and reduced parasitic power loss.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration as claimed in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope herein as set forth in the appended claims and the legal equivalents thereof.
Claims
1. A method for fabricating an integrated LED and LED driver, the method comprising:
- forming an array of LED drivers in a first substrate, wherein the first substrate is a semiconductor substrate;
- forming a bond pad over a top surface of the semiconductor substrate and electrically connected to each LED driver;
- forming an array of LEDs on a second substrate;
- removing a selected LED from the array of LEDs on the second substrate; and
- directly coupling the selected LED to the bond pad to electrically connect the selected LED to a respective LED driver from the array of LED drivers to form an integrated unit, wherein the integrated unit comprises an interconnected LED and LED driver.
2. The method of claim 1 wherein the second substrate is a detachable substrate and wherein a first surface of the array of LEDs is initially coupled to the detachable substrate, the method further comprising:
- attaching a carrier to a second surface of the array of LEDs, the second surface opposite to and substantially planar with the first surface; and
- removing the array of LEDs from the detachable substrate; wherein removing a selected LED from the array of LEDs comprises removing the selected LED from the carrier; and wherein directly coupling the selected LED to the bond pad comprises attaching the second surface of the selected LED to the bond pad.
3. The method of claim 2 wherein forming the array of LEDs further comprises:
- forming a separation layer over the detachable substrate; and
- forming the array of LEDs on the separation layer.
4. The method of claim 3 wherein removing the array of LEDs from the detachable substrate comprises performing a laser separation process to separate the array of LEDs from the separation layer.
5. The method of claim 1 wherein forming the bond pad over the semiconductor substrate and electrically connected to the array of LED drivers comprises forming a reflective bond pad and one or more conductive layers.
6. The method of claim 1 wherein the selected LED is a first selected LED, the respective LED driver is a first respective LED driver, and the integrated unit is a first integrated unit, and wherein the method further comprises:
- removing a second selected LED from the array of LEDs on the second substrate;
- directly coupling the second selected LED to the bond pad to electrically connect the second selected LED to a second respective LED driver from the array of LED drivers to form a second integrated unit; and
- dicing the first substrate to separate the first integrated unit from the second integrated unit.
7. The method of claim 1 further comprising forming a thermal sensor adjacent each LED in the array of LEDs in the semiconductor substrate.
8. The method of claim 1 further comprising:
- depositing a dielectric material over a first surface of the array of LEDs and the top surface of the semiconductor substrate;
- etching a via into the dielectric material to expose at least a portion of the first surface of each LED in the array of LEDs; and
- forming an electrical interconnect in contact with the first surface of each LED in the array of LEDs.
9. A method for fabricating a product with a plurality of integrated LED and LED driver units, the method comprising:
- forming LED drivers in a first substrate, the first substrate being a semiconductor substrate;
- forming bond pads over the semiconductor substrate, wherein each bond pad is electrically connected to a respective LED driver;
- forming LEDs directly on a second substrate;
- removing the LEDs from the second substrate; and
- attaching each LED to a respective bond pad to form the product with the plurality of integrated LED and LED driver units.
10. The method of claim 9 further comprising:
- depositing a dielectric material over the product with the plurality of integrated LED and LED driver units;
- etching vias into the dielectric material, wherein each via exposes a surface of a respective LED; and
- forming electrical interconnects in the vias, wherein each electrical interconnect is in contact with the surface of a respective LED.
11. The method of claim 9 wherein:
- each bond pad has an upper surface;
- each LED has an upper surface and a lower surface; and
- contacting each LED to a respective bond pad comprises contacting the upper surface of each LED to the upper surface of the respective bond pad.
12. The method of claim 9 wherein the second substrate is a detachable substrate and wherein the method further comprises:
- forming a carrier over the LEDs; wherein removing the LEDs from the second substrate comprises removing the LEDs from the detachable substrate before contacting each LED to the respective bond pad.
13. The method of claim 9 wherein forming the LEDs directly on the second substrate comprises forming the LEDs directly on a separation layer over a detachable substrate; and
- wherein removing the LEDs from the second substrate comprises removing the LEDs from the separation layer before contacting each LED to the respective bond pad.
14. The method of claim 13 wherein removing the LEDs from the detachable substrate comprises performing a laser separation process to separate the LEDs from the separation layer.
15-20. (canceled)
21. A method for fabricating an LED, the method comprising:
- forming light emitting structure layers over a second substrate, wherein a bottom surface of a first light emitting structure layer is directly on the second substrate;
- completely dicing each light emitting structure layer and the bottom surface to isolate LEDs, wherein the second substrate is not completely diced;
- attaching a carrier to a top surface of the LEDs; and
- removing the LEDs from the second substrate.
22. The method of claim 21 wherein removing the LEDs from the second substrate comprises uncovering the bottom surface of each LED.
23. The method of claim 21 further comprising:
- forming a LED driver in a first substrate, wherein the first substrate is a semiconductor substrate;
- forming a bond pad over a top surface of the semiconductor substrate and electrically connected to the LED driver; and
- directly mounting the bottom surface of each LED to the bond pad.
24. The method of claim 1 wherein a first surface of the array of LEDs is initially directly coupled to the second substrate, the method further comprising:
- attaching a carrier to a second surface of the array of LEDs, the second surface opposite to and substantially planar with the first surface; and
- removing the array of LEDs from the second substrate.
25. The method of claim 9 wherein a first surface of the LEDs is initially directly coupled to the second substrate, the method further comprising, attaching a carrier to a second surface of the LEDs, the second surface opposite to and substantially planar with the first surface, wherein the carrier supports the LEDs after removing the array of LEDs from the second substrate and before attaching each LED to the respective bond pad to form the product with the plurality of integrated LED and LED driver units.
Type: Application
Filed: Dec 30, 2015
Publication Date: Jul 6, 2017
Patent Grant number: 10297711
Inventor: Donald R. Disney (Singapore)
Application Number: 14/985,220